1. Technical Field
The present disclosure relates to optical apparatuses and, more particularly, to an optical apparatus having a spatial resolution of light emitted from plasma.
2. Description of Related Art
A plasma process has been used in etching or deposition processes for semiconductors, flat-panel displays, solar cells, and so forth. The plasma process may be performed to supply chemical species such as, for example, radicals having high reactivity to a chemical reaction of a wafer or a substrate or to supply ions having kinetic energy. An etching or deposition process may be performed by the chemical species and/or the ions. In this case, predetermined process characteristics may be dependent upon density average and distribution of the ions and/or the chemical species.
When density averages of chemical species are measured, the density of the respective chemical species may be obtained by analyzing emission spectrum emitted from plasma. In an indirect manner, a Langmuir probe is typically used to measure special distribution of chemical species. The Langmuir probe includes a probe, which functions as an electrode and is inserted into a vacuum chamber. For this reason, the Langmuir probe may not be suitable for use during a plasma process.
In addition, there are other measuring apparatuses each using an electrode. For example, a portion of a sensor acting as the electrode is inserted into a chamber. The above-mentioned measuring apparatuses typically all measure change in electrical characteristics of plasma. Accordingly, each of the measuring apparatuses may indirectly measure only density average of all chemical species through electrical characteristics of plasma, not through density of the respective chemical species.